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'Mean axis of rotation of the midtarsal joint' NESTER et al.

Discussion in 'Biomechanics, Sports and Foot orthoses' started by markjohconley, Dec 18, 2017.

  1. markjohconley

    markjohconley Well-Known Member

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    Why would the authors of, "Kinematics of the Midtarsal Joint During Standing Leg Rotation" include in Fig. 2 a, "Mean axis of rotation of the midtarsal joint projected on transverse and sagittal plane".
    Makes no sense doesn't it?, as the MTJ axis depends on which part of the stance phase is occurring.

    Thanks to Mike Weber posting link to article in a 2010 thread, mark

    and a merry xmas to all and their families
  2. Rob Kidd

    Rob Kidd Well-Known Member

    Sorry - is it just me? Can you give a link to their paper? Rob
  3. efuller

    efuller MVP

    When the axis is not parallel to one of the cardinal planes you need to show it in two planes to give its 3 dimensional orientation.

    When we project the STJ axis onto the transverse plane we don't know if the axis is nearly horizontal or nearly vertical. This we can see if we have a sagittal, or frontal, view of the STJ axis. The reason that we use the transverse plane view is that we want to be able to calculate the perpendicular distance from the line of action of ground reaction force. (GRF is mostly vertical and therefore mostly perpendicular to the transverse plane.)
  4. markjohconley

    markjohconley Well-Known Member

    Thanks Eric, wouldn't the GRF always be vertical or did you typo for ORF?
    I should have omitted the, " ... projected on transverse and sagittal plan", as I meant why did they bother with the 'mean' axis. I can not fathom why a 'mean' axis would be of significance if it is not constant during ROM of the joint.
    All the best for xmas to you and your family, mark
    Last edited: Dec 19, 2017
  5. Petcu Daniel

    Petcu Daniel Well-Known Member

    Maybe this is a good aproximation for the foot's joints. 2-3 degrees deviation from vertical I think it counts for more proximal joints.

    GRF is not vertical because there are shear forces which are the horizontal components of the GRF. You have need a force platform to measure all components. Pressure plates takes into consideration only the vertical component of GRF

  6. efuller

    efuller MVP

    This goes to what we use axes of rotation for. One use is to describe the motion that occurs. In that case a mean axis of rotation would be useful. Another use is to calculate joint moments. Knowing an average axis might be good enough to answer a specific question.

    To add to Daniels good answer, Even static stance has a little horizontal force, especially if you stand with your feet wider apart. I recall a paper that had a-p forces at 10% of vertical forces and med-lat forces at 1%. I don't recall if that was walking or running.
  7. markjohconley

    markjohconley Well-Known Member

    Thanks gents.
    I should have realised that there would be horizontal forces as components of GRF. I will have to reread re. ORF components, must have got confused.

    I am still floundering as to why a 'mean axis' is useful as say with Nester's results re. MTJ axis depends on which part of stance; with forefoot contact to heel lift spatial position being (what appears to be) significantly different to before forefoot contact and after heel lift,
    thanks again, mark
  8. Petcu Daniel

    Petcu Daniel Well-Known Member

    I'm sure this article will be of help: In-shoe pressure measurement and foot orthosis research: A giant leap forward or a step too far?", Spooner SK, Smith DK, Kirby KA.
    You'll find it here: https://www.researchgate.net/public...search_A_giant_leap_forward_or_a_step_too_far
  9. efuller

    efuller MVP

    An axis of rotation describes the relative motion between the bone(s) on one side of a joint to the bone(s) on the other side of the joint. A good question is how useful is knowing that particular motion.

    That particular article was useful in questioning the two midtarsal joint axes dogma. The actual axis of motion that was measured was not either the longitudenal or oblique axis that Root et al uses. However, if you understand that an axis of rotation is an imaginary line that describes motion, you don't need this paper to refute theories based on the long and oblique axes of the midtarsal joint.
  10. markjohconley

    markjohconley Well-Known Member

    At any instant in time a joint can only be moving about one (imaginary) axis, yes?

    Also, how can the MTJ have a, " ... actual axis of motion ... ", and is this what Nester et al. refers to as, "... mean axis ... "?
    Wouldn't it be similar for the STJ?
    Thanks Eric.
  11. Petcu Daniel

    Petcu Daniel Well-Known Member

    As the movement is determining the rotation axis I think, from this point of view we can describe two rotations of the talus (for example):
    -rotation around STJA - blue arrow
    -rotation with STJA - red arrow
    Which seems to be confusing!
    upload_2017-12-21_14-59-11.png upload_2017-12-21_15-17-47.png

    Images adapted after:

    Attached Files:

  12. Daniel:

    You are confusing rotational motions of the talus relative to the calcaneus, which determine the STJ axis, with 3D rotations and translations of the STJ axis relative to the ground. They are two very different things.
  13. Mark:

    Yes, at any instant in time the joint can only have one axis of rotation in 3D space. This includes the subtalar joint (STJ) and midtarsal joint (MTJ), along with all other joints of the body. I believe that Nester et al, in referring to a "mean axis", was averaging the axes he measured for the MTJ in this subjects, as the MTJ axis moved in space during the weightbearing activities they were testing.

    The STJ also does not have a singular axis. Rather, the STJ has been shown, in multiple modern scientific research papers to have, rather, a "bundle of axes" which tend to pass through the dorsal talar neck anteriorly and through the posterior calcaneus posteriorly.

    Now, the big difference between the STJ and MTJ is that the bundle of STJ axes that occur during STJ motion is a much "tighter" bundle, than that of the MTJ. The MTJ axis will, in other words, translate and rotate much more in space during weightbearing activities than does the STJ axis. This is due to the fact that the STJ can be considered to be a "tightly constrained joint", more analogous to a slightly sloppy door hinge, while the MTJ can be considered to be a "loosely constrained joint" more like the hip joint or wrist joint, where multiple, widely variant, joint axes may be possible depending on the direction, magnitude and point of application of the external forces acting on the foot.

    You may want to read this thread from a few years back to better understand these concepts.

  14. efuller

    efuller MVP

    What I meant by actual axis of motion was the motion measured over one short time period, or several discrete time periods over a step. It was helpful for me to read the Van Laangallan paper on how he calculated the axis of motion at various points in time. So, the MTJ doesn't have an actual axis of motion. One particular movement of the joint, from one point in time to another point in time, will have an "actual" axis of motion.
  15. Petcu Daniel

    Petcu Daniel Well-Known Member

    The blue arrow is representing the rotation of the talus relative to the calcaneus while the red one is representing the 3D rotation of the STJ axis relative to the ground. The motion of the talus relative to the ground should be described relative to these two rotations.
  16. Rob Kidd

    Rob Kidd Well-Known Member

    MMMmmm, I have been watching this develop - and since I am long retired from anything "biomechanical", it does beg the question - am I entitled to an opinion? However, the one expression missing from this whole page, is that of "instant centres" of rotation. Surely, certainly with regard to large joints such as a knee, it is well known that the joint axis moves as the joint moves. Thus at the the end of the ROM, one has a mean axial position. Now I know that taking this to a midtarsal joint, or even a subtalar joint, maybe taking axial theory one too far, I in reality it should be no different. I now forget where instant centres were first described, possible in Barnet and Napier 1954 in their two axial model of the ankle. It may have been as late and Van Lang, but it is not new. I fail to see why we are having a problem with this (unless I have missed the point, in which case I retract the above). Come back to a large joint like the knee. In its last few degrees of "dorsiflexion" a considerable part of the movement taking place is internal femoral rotation (or external tibial, take your pick), the axis is clearly moving; there is, therefore, no absolute axial position - thus a mean position is described. There is noting new about instant centers, but if I have missed the point, gently push away a proto senile old man!
  17. Petcu Daniel

    Petcu Daniel Well-Known Member

    The best reply which I have is an answer at a biomechanical problem which I've received from Kevin Kirby in Zaragoza a couple of years ago : you've right but how do you teach this? And I think he was right because take a look at the complexity of the problem in two dimensions:
    -instantaneous center of rotation:
    -Four-Bar Mechanism of the Knee:
    -Four-bar linkage: https://en.wikipedia.org/wiki/Four-bar_linkage#/media/File:4_bar_linkage_animated.gif

  18. Axes of rotation within the joints of the body are relatively non-constrained compared to the many axes of rotation within the machines we use on a daily basis (i.e. car axles, drive shafts, steering wheels, bike axles, etc), This means that an external force applied at different angles, with different magnitudes and at different points of application across the joints of the body will produce motion at the joint which does not just follow one "axis" of motion as is commonly taught to first and second year podiatry students.

    The real-life effect of this relative non-constraint within the joints of the body is that variable external force applications across a joint will yield variable axis locations within the joints of the body. The joints of the body that have axis locations that have the "tightest bundle of axes", with the least variability in location in three-dimensional (3D) space, would be considered as relatively constrained joints. Th joints of the body that have axis locations that have the "loosest bundle of axes", with the most variability in location in 3D space, would be considered as relatively non-constrained joints.

    Many machines, such as the example of a car wheel rotating about an car axle, are made of relatively hard materials, such as steel (with an elastic modulus of approximately 200 GPa) that deform little under load and are, therefore, highly constrained. Being "highly constrained" means that regardless of the direction, point of application and magnitude of the external force acting on the wheel of the automobile, the car wheel will still have an axis of rotation that is constant in location (as long as the axle and wheel don't break under the load).

    Now, apply this logic of constrained and non-constrained axes of rotation to the joints of the body. Which joints of the foot and lower extremity are the most constrained and which are the least constrained? My vote for the most constrained joint of the human foot and lower extremity is the subtalar joint (STJ). This means that regardless of the direction, magnitude and point of application of external force acting across the STJ, the 3D location of the axis of rotation of the STJ will form a relatively "tight bundle" of joint axes, such as that described in Van Langelaan's classic thesis (Van Langelaan EJ: A kinematical analysis of the tarsal joints: An x-ray photogrammetric study. Acta Orthop. Scand., 54:Suppl. 204, 135-229, 1983).

    Now, compare this to the midtarsal joint (MTJ) which is a relatively non-constrained joint within the human foot. The relatively non-constrained MTJ will demonstrate widely different 3D locations for its many axes of rotation as the external forces acting across the MTJ are varied in point of application, direction and magnitude. This is evident in Chris Nester's research on MTJ axes and in Van Langelaan's research also.

    Therefore, even though the STJ and MTJ are adjacent to each other and a few of the same bones, the STJ is a relatively constrained pedal joint and the MTJ is relative non-constrained pedal joint due to the differences in their ligament restraint systems and articular surface constructions. The use of the term "constraint and non-constraint" is very useful in understanding the axes of motion of the foot and lower extremity joints since they are not formed from hard steel parts (at 200 GPa), but rather formed of relatively soft bone (at elastic modulus levels of 14-20 GPa) and ligaments (1.2-1.8 GPa) and cartilage (1-10 MPa).

    For those interested in a greater understanding of these terms, the terms "constraint" and "non-constraint" are also used commonly in joint implant design.

    Last edited: Dec 30, 2017

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